Ship stabilization system



y 1967 F. v. PANGALILA 3,322,090

SHIP STABILIZATION SYSTEM Filed Feb. 7, 1966 4 Sheets-Sheet 1 FIG. I.

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INVENTOR Frans V PangaI/la ATTORNEYS y 1967 F. v. PANGALILA SHIPSTABILIZATION SYSTEM 4 Sheets-Sheet 2 Filed Feb.

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INVENTOR Frans M Panga/i/a BY I TTORNEYS y 1967 F. v. PANGALILA SHIPSTABILIZATION SYSTEM 4 Sheets-Sheet 3 Filed Feb. '7, 1966 FIG. 7.

INVENTOR Frans i ll Panga/i/a BY I mfiww w ATTORNEYS SW/ TCH TRANDUCER GYROS COPE May 30, 1967 F. v. PANGALILA SHIP STABILIZATION SYSTEM 4Sheets-Sheet 4 Filed Feb.

Frans l! Panga/i/a ATTORNEYS United States Patent ()fiice 3,322,096Patented May 30, 1967 3,322,090 SHIP STABILIZATION SYSTEM Frans V.Pangalila, Staten Island, N.Y., assignor to John J. McMuilen Associates,Incorporated, New York, N.Y., a corporation of New York Filed Feb. 7,1966, Ser. No. 525,426 18 Claims. (Cl. 114-125) The present inventionrelates generally to ship stabilization and more particularly to animproved apparatus for applying a restoring moment to a ship by themovement of fluid within a tank.

Ships of practically every type encounter the problem of undesirableship motion caused by the surface condition of the water. Depending uponthe type and size of the ship and the operating conditions to which theship is to be subjected, various hull designs are selected to counteractthe tendency of the Water to impart motion to the ship. Due to the greatnumber of variables present and since cyclic wave motion can cause agradual increase in the energy of motion of the ship, hull designprovides only a limited effect in controlling the ship motion. Otherattempts to minimize ship motion in response to wave action include theprovision of stabilization systems which are capable of applying arestoring moment to the ship when it is subjected to the motion.Particular emphasis has been made with respect to improving systems forminimizing roll. Ballast tanks connected by piping and the like havebeen employed in order to transfer water in a manner to generate arestoring moment. Such systems encounter the difficulty of maintainingthe proper phasing between the restoring moment and the motion impartedto the ship. Efforts to employ volumes of air above liquid ballast forcontrolling the ballast have resulted in massive systems which wereuncertain as well as excessively noisy in operation. Efforts have alsobeen directed to providing the ship with fixed or movable fin membersextending from the hull beneath the waterline and adapted to generaterestoring moments from the hydrodynamic forces on the fins accompanyingthe motion of the ship. In certain applications, controlled fins havebeen effective in controlling the roll of the ship but only at theexpense of coupled-systems employing massive fin members and operatingmachinery.

Present day efforts in the art include stabilization systems employingthe free-surface principle of operation, and although quite successful,they usually include tanks having specially shaped configurations,and/or substantial internal structure involving large amounts ofmaterial that is costly both in terms of money and in weight. This, ofcourse, requires special machinery for making the tanks and, in manycases, reworking of the ships structure to accommodate such tanks.Further, present day designs are limited in adjustability ofstabilization. That is, prior art stabilization systems are usuallydesigned for a specific application or size vessel. Once'installed, theyare not adaptable for a different application Without major remodelinginvolving great expense in terms of time and money to the ship owner.

The present invention is an improvement over the prior art in that ithas built-in versatility while maintaining simplicity of design.

In the principal embodiment of the invention, the ship stabilizingsystem includes a tank entirely passive in design and containing aquantity of fluid having a free surface. The longitudinal axis of thetank is adapted to extend substantially horizontally and substantiallyat right angles to the axis about which the ship is to be stabilized.

Mounted Within the tank is a deflecting plate secured vertically anddisposed so that it converges toward one tank wall while diverging fromthe oposite wall. Thus,

the plate is so oriented with respect to the walls parallel to thelongitudinal axis of the tank, that an oblique angle is formedtherebetween. With the plate mounted in the tank at an oblique angle,the fluid moves in part with a gradually decreasing width. In thismanner, the effective longitudinal dimension of the tank is changed and,therefore, the frequency can change. Thus, in response to smaller rollsof the ship, the fluid can flow back immediately without having to firstreach one or the other tank ends.

The plate may assume a variety of shapes and constructions, all designedto efi'iciently adapt to varying conditions of the sea and best suit theneeds of various ships.

Thus, other embodiments include smoother or hydrodynamically designedtanks, plates and/or the additions of guide plates in the tanks forsmoother fiow of the stabilizing liquid.

Another embodiment includes pivotally mounting the plate to the tankbottom to adjust the oblique angle thereof. The plate can either beadjusted to a position to provide a tank tuned for optimum stabilizingcharacteristics for a particular ship or weather condition encountered,or include a powered control and sensing mechanism to automaticallyadjust the oblique angle and tune the tank as the ship rolls.

A further embodiment includes cutting holes in the plate for controllingthe tuning and damping effects of the plate. The holes may be of apermanent nature, or their efiect may be controlled by adjusting theirtotal area, or their total number as depicted in still furtherembodiments.

In a further embodiment, the tank is converted to a semi-activestabilizing system by including in addition to the deflecting plate, apowered water-moving device such as propellers immersed in the liquiddriven at a constant speed, or to an active system wherein the speed ofthe propellers is controlled by a sensing mechanism.

Accordingly, it is a primary object of this invention to provide a shipstabilizer of simple design which is capable of applying a restoringmoment to a ship.

Another object of this invention is to provide a ship stabilizeremploying essentially one internal component position within an enclosedtank containing a stabilizing liquid having a free surface.

A further object of this invention is to provide a passive shipstabilizer that can be converted to a semi-active stabilizing systemthat is relatively simple in design, and does not require complicatedand cumbersome additional structure.

A yet further object of the present invention is to provide a passiveship stabilizer that can be converted to an active ship stabilizer ofsimple design that can automatically adjust and tune itself to shiproll.

Yet another object of this invention is to provide a passive shipstabilizer that is controllably tunable for various sea and weatherconditions.

It is still a further object of this invention to provide a shipstabilizer that is versatile and easily adaptable to ships or boats ofvarious sizes.

An even further object of the preseint invention is to provide a shipstabilizer that is self-contained and does not require major alterationsin the ships structure for installation.

A still more obvious object of this invention is to provide a shipstabilizer which is compact and reasonably light in Weight.

Other objects and features of the invention will become apparent in thefollowing specification, claims, and drawings in which;

FIG. 1 shows a plain view of the invention containing the tank and theoblique plate;

FIGS. 2a, b and show side elevations of the various profiles that theplate in FIG. 1 may assume;

FIGS. 3a, b and 0 show plan views of various modifications of theembodiment disclosed in FIG. 1;

FIGS. 4a, and b show a semi-active system by including an additionalmechanism to control directional movement of the stabilizing liquid;

FIG. 5 shows the plate having holes cut in it and a control mechanismfor varying the area of said holes; and

FIG. 6 shows the plate with holes cut in it having a control mechanismfor varying the number of holes exposed on said plate;

FIG. 7 shows an active or semi-active embodiment of the invention.

Referring to FIG. 1, a tank 10 has its longitudinal axis substantiallyhorizontal and at right angles to the axis about which the ship is to bestabilized. Mounted within the tank partially filled with stabilizingliquid is a deflecting plate 11 secured vertically and disposed so thatthe end portions converge toward opposite tank walls, thereby forming anoblique angle therebetween. As the ship rolls, most of the stabilizingliquid is channeled in a converging path formed by the plate andrespective side wall and tank 10. In this manner, the liquid movessubstantially in a circular path as indicated by the arrows.

Referring to FIG. 2a, a side elevation of FIG. 1, taken along lines 2-2,shows plate 11 running the full height of tank 10. 7

Referring to FIG. 2b, the static level of stabilizing liquid 20 isslightly above or higher than the height of plate 11. In thisembodiment, there is a constant spillover of stabilizing liquid from onechannel to the other in response to ship roll. It is obvious from thisembodiment that the stabilizing liquid would reach the tank ends morequickly since part of the liquid would be taking a short cut over plate11.

FIG. 2c shows a compromise between the two heights shown in FIGS. 2a and2b. In FIG. 20, plate 11 begins with a height approximately equal to thestatic level of the liquid at the end portions and gradually rises tothe full depth of the tank at its mid-portion. In this way, the plate istuned to provide spillover of the stabilizing liquid during more violentrolls of the ship, where more rapid cross-transfer of the liquid wouldmost likely be needed.

FIGS. 3a and 3b show other configurations in which FIG. 1 may take. InFIG. 3a, the side of tank 10 assume the form of a parallelogram, whileplate 11 runs approximately at right angles to the roll axis of theship.

In FIG. 3b, the tank as shown with rounded corners,

and the cross-section of plate 11 has a flattened S shape for smootherflow of stabilizing liquid 20. Guide plates 11" may be added to aidstill further in the smoother flow of the liquid. It should be notedthat the feature shown in FIG. 3b may be incorporated either singly orin combination with any of the other embodiments disclosed herein.

FIG. 30 has oblique plate 11 mounted on a vertically disposed rotatableaxle 12 located at its mid-portion for adjustment of the oblique angle.By adjusting the oblique angle, the tuning and dampening effects ofplate 11 and thus, the stabilizing effects of tank 10, may becontrolled. Accordingly, plate 11 is adjusted to an angle that providesoptimum stabilizing characteristics for a particular ship or weathercondition encountered. The embodiment shown in FIG. 3c may be convertedto a fully active stabilizing system that automatically controls oradjusts the oblique angle of plate 11 as a function of ship roll. Thisis done by switching in a sensing and control apparatus connected toaxle 12 of plate 11. A gyroscope 30 is connected to a transducer 32.Transducer. 32 puts out an electrical signal, the voltage of which isdirectly proportional to the magnitude of ship roll, to control a motor36 through an amplifier 33 and switch 34. Switch 34 is used todisconnect or connect the sensing mechanism to the control mechanism.

Referring to FIG. 4a, two one-way flap valves are connected, each ofwhich extends from a respective side of plate 11 to an adjacent sidewall of tank 10 to maintain the flow of stabilizing liquid 20 in acircular path in a manner to be explained and as indicated by the arrows6. Flap valves 40 and 42 are for-med from a plurality of horizontallymounted pivotal slats that open and close in only one direction. Theslats overlap one another in single fashion when the valves are closed,and swing open in response to gravity and liquid force to present aplurality of ladder-like horizontal openings that have a dampeningeffect on stabilizing liquid 20 flowing therethrough.

Arrows 8 indicate the direction of roll experienced by tank 10 in FIG.4a. Thus, when the ship rolls starboard,

as shown, flap valve 40 opens to allow free passage of the stabilizingliquid, while flap valve 42 located on the reverse side of plate 11 isforced closed by the combination of gravity and the liquid force'against it. When the ship rolls to port or in the opposite directionfrom that shown by arrows 8, valve 42 will open while valve 40 will beheld closed. Thus, referring to FIG. 4b, the liquid is forced to flowalong one side of tank 10 during roll in one direction and flow alongthe other side of tank 10 during roll in the opposite direction,resulting in a circular path as indicated by arrows 6.

FIGURE 5 shows plate 11 having holes 16 cut therearea of the holes. Bycontrolling the area of the holes, a

tuning and damping may be changed according to cargo carried orprolonged sea conditions.

FIGURE 6 shows a variation of FIG. 5. Instead of controlling the area ofthe holes, the number of holes can be controlled to achieve the sameresult. Thus, control mechansim 18 operatively attached to shutters 16slide on tracks 19 to block or unblock holes 21.

Although the embodiments depicted in FIGS. 5 and 6 are passive innature, i.e., the control mechanism preadjusted and tuned for optimumstabilization, they may be easily converted to fully active systems byswitching in a sensing mechanism (not shown) similar to the onedisclosed in FIG. 3c.

Referring to FIG. 7, a pair of propellers are inserted betweenrespective side walls of tank 10 and plate 11. The embodiment shown inFIG. 7 forms a semi-active stabilization system when propellers 50 and52 are driven at a constant rate causing stabilizing liquid 20 to movein a circular path as described with reference to FIG. 4;

The embodiment in FIG. 7 may be converted into a fully active system byswitching in, via switch 34, the sensing mechanism made up withgyroscope 30, transducer 32, amplifier 33, and similar in operationtothe one disclosed in FIG. 3. Thus, propellers 50 and 52 rotate as afunction of the sensing mechanism which is controlled by the roll motionmade by the ship, e.g., the greater the roll of the ship, the greaterthe speed of the propellers.

'Under thepassive stabilizing mode of operation, the

' dimension together with the level of the liquid. The size and typecargo the ship carries might best aid is considering the size tank to beconstructed.

Referring to FIG. 1, tank 10 operates by stabilizing liquid 20 in tank10 moving in part'with'a gradually de-,

creasing width. In so doing, the effective longitudinal dimension oftank 10 is changed and, therefore, the frequency can change. Therefore,with gentle rolls, liquid 20 in tank may impart a stabilizing effectwithout having to flow to one end or the other of the tank.

The height of plate, 11 in tank 10 determines the dampening effect onthe liquid which in turn determines the'magnitude of the stabilizingmoment produced. In FIG. 2a, greater dampening takes place which resultsin the production of a smaller stabilizing moment. In FIG. 2b, thereverse occurs with a greater stabilizing moment produced because of thedecrease in liquid dampening by plate 11, while in FIG. 2c, acombination of the two results. Thus, in FIG. 2c, with more gentlerolls, a stabilizing effect similar to FIG. 2a is produced, while withmore violent rolls, greater stabilizing moments similar in efiect toFIG. 2b are produced. The type ship employed or personal preference willdetermine which plate (FIG. 2a, b or c) is used.

Under the semi-active mode of operation, the same tuning parametersexist that existed for the passive stabilizing system except that thevolume or level of the liquid is less critical. FIG. 4, and FIG. 7 withthe sensing mechanism disconnected are examples of the ship stabilizingsystem according to the present invention operated in the semi-activemode.

In FIG. 4, a semi-active system is created when the ship roll incombination with flap valves 40 and 42 cause liquid 20 to be damped andflow in a circular motion in a manner described hereinabove. Because ofthe structure of the present invention, the liquid can flow in acircular path around the oblique plate (as opposed to merely a to andfor movement) without any detrimental eiTect to the systems operation.Thus, simple one-way flap valves (40 and 42) can he and are utilized toaid in providing the required dampening effect on the liquid as it flowsthrough the valves nozzle-like horizontal openings. The tuning efiect ofthe valves in the system is described in the operation descriptiondirectly below with regard to the semi-active mode of operation for thepropellers of FIG. 7.

In FIG. 7, the propellers driven at a constant speed to maintain theliquid in a circular movement around the plate during all phases of shipmotion form a semi-active stabilization system. Again, because thestructure of the present invention allows circular movement of theliquid, simply constructed propellers that operate at a constant speedrequiring no speed adjustment mechanisms or reversing mechanisms areused.

During no roll periods, there are no upsetting moments produced on theship because any force created at one end of tank 10 by the movingliquid is cancelled at the other end of tank 10. During extended periodsof no roll activity by the ship, the liquid ceases its circular movementin FIG. 4 by being damped out, and the power to the propellers in FIG. 7may be cut off.

In operation, if the ship rolls starboard, all the liquid flowsstarboard. But plate 11 in combination with the flap valves of FIG. 4,and plate 11 in combination with the propellers of FIG. 7, cause theliquid to decelerate on the aft side of the tank and accelerate at thefore side. Thus, by referring to FIGS. 4b and 7, essentially no motionis produced on the aft side of tank 10, and tuned motion is produced onthe fore side. If the ship then rolls to port, essentially no motion isproduced on the fore side of tank 10, and tuned motion is produced onthe aft side.

Thus, because of the circular movement of the liquid, tuning of the tankin a semi-active mode of operation as disclosed in FIGS. 4 and 7 isaccomplished simply and efiiciently without having to resort tocomplicated and/or other machinery that would otherwise prove necessaryto control the liquid movement and tune a semi-active (or active) shipstabilization system.

Under the active mode of operation, the same tuning parameters applythat applied to the semi-active mode of operation. The active mode ofoperation allows the stabilization system according to the presentinvention to be totally sensitive and responsive to the motions of theship.

In FIGS. 3(0), 5, 6 and 7, upon switching in the sensing mechanism,described hereinabove, any roll motion by the ship is picked up by thesensing mechanism and is automatically reacted to by the respectivecontrol mechanisnis shown. In FIG. 30, the angle of plate 11 is changed;in FIGS. 5 and 6 (sensing mechanism not shown) the area and number ofholes in plate 11 are changed respectively; and in FIG. 7, the speed ofthe propellers changes. The aforementioned changes produce eithergreater or less dampening on the stabilizing liquid which result inconstant tuning of the system to stabilize against the initiatingcauses. Thus, by the addition of relatively standard sensing and controlequipment, the passive and/or semi-active stabilization systemsaccording to the present invention are easily and efliciently convertedto fully active stabilization systems.

While there has been disclosed what at present are considered to be thepreferred embodiments of the invention, it is to be understood thatchanges and modifications can be made therein without departing from theessential spirit and scope of the invention as presented in the appendedclaims.

What is claimed is:

1. A passive stabilization system for a ship comprising a tank having abottom, first and second sides, and two ends and having its longitudinalaxis mounted transversely to the roll axis of said ship, said tankpartially filled with a predetermined amount of liquid, an elongatedupstanding plate means having a first and second end, said plate meansmounted in said tank with its longitudinal dimension extending generallylongitudinally in said tank and with said ends terminating short of saidtank ends, said first end of said plate spaced closer to said first sideof said tank than to said second side, and said second end of said platespaced closer to said second side than to said first side so that anoblique angle is formed between said plate and either of said tanksides.

2. The apparatus as claimed in claim 1 wherein said plate means has aheight extending at least above the static level of said liquidpartially filling said tank.

3. The apparatus as claimed in claim 1 wherein the static liquid levelpartially filling said tank is at least slightly above the height ofsaid plate means.

4. The apparatus as claimed in claim 1 wherein said plate means has aheight whose end portions extend substantially equal to the static levelof said liquid partially filling said tank and whose midportion extendsthe full depth of said tank.

5. The apparatus as claimed in claim 1 wherein said plate means has alongitudinal cross-section in the shape of a flattened S.

6. The apparatus as claimed in claim 1 wherein said plate meansadditionally includes as part of the structure thereof guide plate meanshydrodynamically shaped and mounted within said tank for cooperatingwith said liquid.

7. The apparatus as claimed in claim 1 wherein said tank includesrounded corners.

8. The apparatus as claimed in claim 1 including a pair ofunidirectional liquid flow means each inserted vertically in said tankand extending perpendicularly from the side walls of said tank to theelongated side surfaces of said oblique plate adjacent said tank sidewalls, said means placed so as to allow said liquid to flow in acircular movement around said plate.

9. The apparatus as claimed in claim 8 wherein said unidirectionalliquid flow means comprises a plurality vertically spaced andhorizontally displaced pivotal slats that swing open and closed in onlyone direction, said slats being in overlapping configuration in theclosed position and forming a plurality of ladder-like horizontalopenings in the open position.

10. The apparatus as claimed in claim 1 wherein said plate means ispivotally mounted to the tank bottom so that said oblique angle isadjustable.

11. The apparatus as claimed in claim 10' further i-n eluding means toautomatically adjust said oblique angle as a function of ship roll.

12. The apparatus as claimed in claim 1 wherein said plate meansincludes a plurality of openings at both ends and spaced equidistantfrom the mid-line of said plate means.

13. The apparatus as claimed in claim 12 wherein said plate meansincludes shutter means for controlling the number of openings exposed.

14. The apparatus as claimed in claim 13 further including means foroperating said shutter means in response to ship roll.

15. The apparatus as claimed in claim 12 wherein said plate meansincludes means for controlling the area of said openings.

16. The apparatus as claimed in claim 15 further including means foroperating said area controlling means in response to ship roll.

17. The apparatus as claimed in claim 1 further includ! ing poweredwater-moving means at least partially immersed in said liquid to controlthe liquid movement in a predetermined manner. 7

18. The apparatus as claimed in claim 17 wherein said power meansoperates in response to ship roll.

No references cited.

MILTON BUCHLER, Primary Examiner.

T. M. BLIX, Assistant Examiner.

1. A PASSIVE STABILIZATION SYSTEM FOR A SHIP COMPRISING A TANK HAVING ABOTTOM, FIRST AND SECOND SIDES, AND TWO ENDS AND HAVING ITS LONGITUDINALAXIS MOUNTED TRANSVERSELY TO THE ROLL AXIS OF SAID SHIP, SAID TANKPARTIALLY FILLED WITH A PREDETERMINED AMOUNT OF LIQUID, AN ELONGATEDUPSTANDING PLATE MEANS HAVING A FIRST AND SECOND END, SAID PLATE MEANSMOUNTED IN SAID TANK WITH ITS LONGITUDINAL DIMENSION EXTENDING GENERALLYLONGITUDINALLY IN SAID TANK AND WITH SAID ENDS TERMINATING SHORT OF SAIDTANK ENDS, SAID FIRST END OF SAID PLATE SPACED CLOSER TO SAID FIRST SIDEOF SAID TANK THAN TO SAID SECOND SIDE, AND SAID SECOND END OF SAID PLATESPACED CLOSER TO SAID SECOND SIDE THAN TO SAID FIRST SIDE SO THAT ANOBLIQUE ANGLE IS FORMED BETWEEN SAID PLATE AND EITHER OF SAID TANKSIDES.